Last night MODX Revolution 2.5.2 came out. This is a critical security upgrade for all versions, and you need to go update your MODX sites.
Seriously, go update your sites. Right. Now.
All sites upgraded?
Well done! You can read the MODX.com announcement here.
Over the next few days more information about the fixed vulnerabilities will become available. For now, you just need to make sure all your MODX Revolution sites are on 2.5.2.